1. Field
The disclosure relates to a method, system, and article of manufacture for copying of data in a remote storage unit.
2. Background
Information technology systems, including storage systems, may need protection from site disasters or outages, where outages may be planned or unplanned. Furthermore, information technology systems may require features for data migration, data backup, or data duplication. Implementations for disaster or outage recovery, data migration, data backup, and data duplication may include mirroring or copying of data in storage systems. Such mirroring or copying of data may involve interactions among hosts, storage systems and connecting networking components of the information technology system.
An enterprise storage server (ESS), such as the IBM* TotalStorage Enterprise Storage Server*, may be a disk storage server that includes one or more processors coupled to storage devices, including high capacity scalable storage devices, Redundant Array of Independent Disks (RAID), etc. The enterprise storage servers are connected to a network and include features for copying data in storage systems. *IBM, IBM TotalStorage Enterprise Storage Server, Enterprise System Connection (ESCON), OS/390, Peer to Peer Remote Copy (PPRC), FlashCopy are trademarks of International Business Machines Corp.
Enterprise storage servers may include copy functions for copying data either locally, i.e., within the same on-site ESS, or remotely, i.e., copying data to a separate remote-site ESS. The copy functions can be classified as either dynamic or point-in-time copy functions. Dynamic copy functions constantly update the secondary copy as applications make changes to the primary data source. Point-in-time copying techniques provide an instantaneous copy or view of what the original data looked like at a specific point in time.
In certain enterprise storage servers there may be copy functions, such as, FlashCopy*, that provide a point-in-time copy of the data. Implementations may copy data between a set of local/source volumes and a corresponding set of remote/target volumes in enterprise storage servers. FlashCopy may provide a point-in-time copy for ESS volumes by creating a physical point-in-time copy of the data, with minimal interruption to applications, and make it possible to access both the source and target copies substantially immediately. Both the source and the target volumes reside on the same ESS system, although implementations may be possible where the source and target volumes reside on different ESS systems. *IBM, IBM Total Storage Enterprise Storage Server, Enterprise System Connection (ESCON), OS/390, Peer to Peer Remote Copy (PPRC), FlashCopy are trademarks of International Bussiness Machines Corp.
Peer-to-Peer Remote Copy (PPRC) is an ESS function that allows the shadowing of application system data from a first site to a second site. The first site may be referred to as an application site, a local site, or a primary site. The second site may be referred to as a recovery site, a remote site, or a secondary site. The logical volumes that hold the data in the ESS at the local site are called local volumes, and the corresponding logical volumes that hold the mirrored data at the remote site are called remote volumes. High speed links may connect the local and remote ESS systems.
In the synchronous type of operation for PPRC, i.e., synchronous PPRC, the updates done to the local volumes at the local site are synchronously shadowed onto the remote volumes at the remote site. As synchronous PPRC is a synchronous copying solution, write updates are ensured on both copies (local and remote) before the write is considered to be completed for the application. In synchronous PPRC the application does not get the “write complete” condition until the update is synchronously done in both the local and the remote volumes. Therefore, from the application perspective the data at the remote volumes at the remote site is real time data always consistent with the data at the local volumes.